Re: [Data Cubes] unit of measure with multiple measures

Ok, Dave,

I think I understand now.
If I have a multiple measure observation with different UoMs I have to
split it so that each obeservation has only one UoM for all its
measures, right?

Somehow I dislike this. F.e. we have observations of chemical exposure
including number of probands (count), arithmetic mean (ng/g dw) and
standard deviation (ng/g dw).

So I need to describe this in two separate qb:Observation instances, one
with number of probands and UoM "count", and one with arithmetic mean
and standard deviation, both with UoM "ng/g dw", right?

This somehow tears the real obeservation into tatters for the sake of a
in-my-eyes strange data model.
Why not describe each single measure as a pair of number and UoM?
Is there a really serious reason?

Best,
Thomas

Am 19.07.2012 10:15, schrieb Dave Reynolds:
> Hi Thomas,
>
> On 18/07/12 17:30, Thomas Bandholtz wrote:
>> Hi,
>>
>> i am dealing with multiple measures and i want to give them
>> individual uoms.
>> http://www.w3.org/TR/vocab-data-cube/ is a little bit vague about this.
>> I read: "Specifically in this example we can use the predefined
>> sdmx-attribute:unitMeasure which in turn corresponds to the COG concept
>> of UNIT_MEASURE."
>>
>> and later:
>>
>> "Attributes can also be attached directly to the qb:MeasureProperty
>> itself (e.g. to indicate the unit of measure for that measure) "
>
> Indeed you can attach sdmx-attribute:unitMeasure to the
> qb:MeasureProperty (if you declare that as the attachment level) or to
> the observation (if you use the measure dimension approach to
> multi-measure cubes).
>
>> I want to provide a qb:codeList with a set of uoms, but the schema says
>> i can do this only with a qb:DimensionProperty, why?
>
> No, it's the other way round.
>
> The schema requires qb:DimensionProperty to be coded (and that's one
> of the restrictions under review in GLD) but it is doesn't prevent
> other uses of CodedProperty.
>
> qb:ComponentProperty > qb:CodedProperty > qb:DimensionProperty
>                      > qb:AttributeProperty
>                      > qb:MeasureProperty
>
> There's no disjointness assertions between qb:CodedProperty and the
> others. Something can't be both a qb:DimensionPropety and  a
> qb:AttributeProperty but it can be both a qb:CodedProperty and
> qb:AttributeProperty.
>
> So if you have a qb:AttributeProperty you want to want to use to
> declare the UoM and you want to declare those as skos:Concepts then
> you can indeed use qb:codeList to associate the skos:ConceptScheme for
> the UoMs with the qb:AttributeProperty.
>
> However, for declaring units of measure you might want to consider
> using an existing vocabulary. In particular we've found QUDT [1][2]
> very useful and adds more value than a simple concept scheme.
>
> Dave
>
> [1] http://www.qudt.org/
> [2] http://www.linkedmodel.org/catalog/qudt/1.1/index.html
>
>
>
>


-- 
Thomas Bandholtz
Principal Consultant

innoQ Deutschland GmbH
Krischerstr. 100, 
D-40789 Monheim am Rhein, Germany
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thomas.bandholtz@innoq.com
+49 178 4049387

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https://github.com/innoq/iqvoc/wiki/Linked-Data (English)

Received on Friday, 20 July 2012 11:32:23 UTC